Not really into optics, but generally speaking we see things because light reflects off the objects and it enters our eyes which helps us form a picture of the object. Hence why we can't see anything in total darkness because there's no light being reflected.

In a normal window, when the light hits the glass, some light rays are reflected back, and some go through it and reflect off the objects. This is why we can usually make out that there is a window (the glass) and we can also see what's inside. In a tinted window, I'm guessing most or all of the light is reflected back by the coating, no light rays pass inside. So we cannot see what's behind it.

Don't quote me on this though =P, definitely look it up.

P.S Ever seen people walk straight in to glass doors? When they are really clean it can sometimes be quite difficult for the eye to see there is indeed a glass door because a lot of the light refracts straight through, and not enough reflects back for the eye to pick up and make a distinction that there is a glass door.

\P.S Ever seen people walk straight in to glass doors? When they are really clean it can sometimes be quite difficult for the eye to see there is indeed a glass door because a lot of the light reflects straight through, and not enough reflects back for the eye to pick up and make a distinction that there is a glass door.